Substantial decrease of heat-shock protein 90 precedes the decline of sperm motility during cooling of boar spermatozoa.

摘要

The aim of this study was to evaluate the changes in protein profile of boar spermatozoa during the process of cooling and freezing. Semen samples were collected from 9 sexually mature boars and samples for protein analysis were obtained before chilling, after cooling to 15deg C, after cooling to 5degree C, after thawing of semen frozen to -100degree C and after thawing of semen stored at -196degree C for 1 week. Semen characters evaluated included progressive motility and the percentage of morphologically normal spermatozoa. Proteins from 5 X 106 spermatozoa were separated and analysed by SDS-PAGE. There was a marked decrease in a 90 kDa protein in frozen-thawed spermatozoa. Western blot analysis revealed that this protein was the 90 kDa heat shock protein (HSP90). Timecourse studies showed that the decrease of HSP90 in spermatozoa occurred in the first hour of cooling to 5degree C, there being a 64% decrease in HSP90 in spermatozoa cooled to 5degree C compared with fresh spermatozoa before chilling. However, the motility and the percentage of normal spermatozoa did not decrease at this time. Both sperm parameters declined markedly in semen thawed after freezing to -100degree C. It is suggested that the decrease in HSP90 precedes the decline in sperm characters, and that there is a timelag of 2-3 h between the decrease in HSP90 and decline in sperm motility.